In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving data rates, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing data rates, providing low delay and so on, long-term evolution (LTE) has been under study (see Non Patent Literature 1).
In a third-generation system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. In an LTE system, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. In the UMTS network, successor systems to LTE are also under study for the purposes of achieving further broadbandization and higher speed (for example, LTE advanced (LTE-A)).
In the LTE system, there is a promising technique to improve system performance even more, called “inter-cell orthogonalization”. For example, in the LTE-A system, intra-cell orthogonalization is made possible by orthogonal multiple access both on the uplink and on the downlink. That is to say, on the downlink, orthogonality is established between user terminals UE (user equipment) in the frequency domain. In the meantime, between cells, like in W-CDMA, interference randomization by one-cell frequency re-use is fundamental.
Then, in 3GPP (3rd Generation Partnership Project), Coordinated Multi-Point transmission/reception (CoMP) is under study as the technique for realizing inter-cell orthogonalization. In this CoMP, a plurality of cells coordinates to perform signal processing of transmission and reception for one or a plurality of user terminals. For example, as for the downlink, study has been made of simultaneous transmission from a plurality of cells to which precoding is applied, and coordinated scheduling/beamforming. By application of these CoMP techniques, improvement is expected of throughput performance particularly of a user terminal UE at a cell edge.